Background

Carrion is a nutrient- and energy-rich resource that is used by a variety of organisms, particularly carnivorous vertebrates, arthropods and microbes. It can influence the movements and spatial distribution of scavenging species and, as many scavengers are also predators, the presence of carrion may have cascading effects on live prey.

The degradation of a carcass further influences soil properties, as well as the growth of certain plant species in the vicinity of the resource. Thus, carrion has the potential to affect many aspects of community ecology, and to play key roles in nutrient cycling and in shaping food-web dynamics through both direct and indirect pathways.

But despite the potential community-wide impacts of this resource, carrion ecology remains understudied, and research on the topic is primarily northern hemisphere based.

A new project to fill the knowledge gaps

Project OzScav’s main directive is to investigate the role of carrion in ecological communities in Australia.

Specifically, this project:

(1) explores how carrion is used by Australian vertebrates, arthropods and microbes,

(2) determines whether the presence of carrion has cascading impacts on surrounding live prey, and

(3) examines the effects of carrion on soil nutrients and subsequent plant growth surrounding the resource.

The project currently spans three study systems across Australia, representing temperate, subalpine and desert biomes.

Data are providing insight into the role of carrion in Australian food-webs, and, as study locations are situated on National parkland and conservation reserves, data are also contributing directly to local land management (e.g. by informing land managers of the potential impacts of carcasses left to lie in the environment following culling events).

Project updates as well as student and volunteer opportunities will be posted on this website, via my own twitter account (@NewsomeTM) and via the twitter account of Emma Spencer who is a PhD student on the project (@EE_Spencer).

Happened across a hungry lace monitor (Varanus varius) feeding at the remains of an eastern grey kangaroo. These animals are major summer-time scavengers in the Wolgan Valley (although they are proving quite difficult to capture on remote cameras!). pic.twitter.com/152RGLQqUi

And, thankfully, surviving the academic job market by securing an ongoing position as Lecturer (Academic Fellow) at The University of Sydney. I will commence in January 2018 after my Deakin University Fellowship has ended. Thank you Deakin for the support and great research environment over the last two years.

The letter calls on the Federal Government to reverse its decision to cease funding Australia’s Long Term Ecological Research Network (LTERN). The network comprises more than 1100 long-term field plots across Australia, including those in the Simpson Desert (pictured above) where I have conducted research in collaboration with the Desert Ecology Research Group at The University of Sydney.

The existing program receives $900,000 of support from the Federal Government’s Terrestrial Ecosystem Research Network (TERN). This support is being slashed at a time when even the USA is increasing funding for its own network by US$5.6M annually.

Hopefully a last ditch bid to the Federal Government by those who administer and lead LTERN will result in a reversal of this decision, and even better, an expansion of the program.

“This gem of a book about Australia’s iconic symbol, the red kangaroo (Osphranter rufus; formerly Megaleia rufus, Macropus rufus; Jackson and Groves 2015), will serve as an inspiration to younger field-oriented mammalian ecologists and equally admired by more seasoned ones. It is a newly polished chronicle of an unfinished manuscript of pioneering field research conducted by Alan Newsome in Central Australia between 1957 and 1962, a region that then was still in a frontier state. The research took place when Alan was fresh out of the University of Queensland with just an undergraduate science degree. Alan had contracted with the Animal Industry Branch of the Northern Territory Government to learn all he could about the life history of the red kangaroo and its interactions with cattle in the arid interior of the Northern Territory, while other ecologists were conducting comparable studies in Western Australia, South Australia, and New South Wales.

It is unclear when Alan began drafting this manuscript, but the last dated correspondence with a potential publisher, Collins Publishing, was 1975. For reasons unknown, the manuscript was placed in storage at his home in Canberra, and was not refound until 2010, following Alan’s untimely death from Alzheimer’s disease in 2007. The manuscript and various notes and colored slides were discovered amongst his belongings by his wife Jane Thompson, and his son Thomas Newsome; Thomas is a promising young ecologist in his own right, with extensive field experience in the Northern Territory’s arid heart, and therefore all the more suited to see the manuscript through to publication. In so doing, Thomas sought faithfully to retain his father’s writing style, and transcribed the 6 manuscript chapters pretty much verbatim, even though they varied in their completeness from near final drafts to hand-scrawled notations.

From this has emerged a narrative description of a monumental 6-year ecological study in Central Australia, under the harshest of conditions of drought – summer daytime temperatures sometimes reaching 50 C – undertaken by a young man who, at its inception, was age 22. Provided with a four-wheel drive vehicle, access to a light airplane and pilot, a skilled rifle marksman, and indigenous aboriginal aids and informants, it still required a leader with exceptional organizational skills to design and execute the scale of study the goals demanded; that leader was the young Alan Newsome, who more than met those goals. In so doing, Alan established a study area in a vast region on the Burt Plain to the north of the MacDonnell Ranges that lie to the north and west of Alice Springs, N.T. The study area comprised 4 recognizable land-systems with discernible but overlapping plant components that lent themselves both to aerial surveys for kangaroo distribution and abundance, and ground-based collections for necropsy analysis of reproductive and physical condition; these studies spanned climatic events of prolonged drought finally broken by abundant rainfall over a region where, concomitantly, cattle grazed.

Repeated flights over fixed aerial transects during the study period revealed that these grass-dependent marsupials prefer to remain in the vicinity of mulga (Acacia aneura) woodlands, where their primary food, green grass, abounds in periods of normal rain; but, as drought ensues and these grasses dry up, there is a mass movement toward and into the open plains, where there are widely scattered seeps and springs which also attract cattle. There the cattle graze on the drying grass, which stimulates vegetative regrowth providing the kangaroos with a continuing supply of green food until the next rain cycle; then they will move back into the woodlands. Thus kangaroos, if anything, benefit from the presence of cattle during drought.

Between 1958 and 1963 a system of random ground sampling of red kangaroos was established at night along fixed transects in woodlands and open plains during and following drought, by spotlighting randomly selected animals from a vehicle; these were then shot to assess reproductive condition and physical state. About 2000 kangaroos were collected from which stomach samples and reproductive tracts were preserved for analysis. Stomach analyses confirmed that green grasses comprised the kangaroos’ diets, even during drought. Reproductively, female red kangaroos nearly always had a suckling joey either in the pouch or at foot, as well as an embryonic blastocyst in an arrested state of development (i.e. diapause) in the uterus; this latter condition was described earlier in detail in a small wallaby (the quakka) by Sharman (1954), and likely is characteristic of macropods in general. Continued development of the blastocyst occurs only following cessation of nursing of the preceding joey, either through weaning or death. Upon birth of a near-embryonic fetus, the mother kangaroo undergoes ovulation and postparturient mating, assuming a fertile male is present. Thus, even during severe drought resulting in a joey’s death, another replacement young is soon present to increase the probability of population survival. In a sense then, this macropod capacity of arrested development is a preadaptation for surviving drought, even though other circumstances may have stimulated its original evolution. In the males spermatogenesis resulting in fertility seemed to be unaffected by drought, except during the hottest, prolonged summer periods when some kangaroos in the open plains were without shelter, and unable to regulate testicular temperature compatible with sperm production; but even during these summer droughts at least some fertile males were always present, ensuring successful reproduction.

Alan also draws attention to the advantages during drought of the female kangaroo’s gestational characteristics compared to those of a cow, when both are competing for the same diminishing supply of grass. The kangaroo has a gestation period of only 5 weeks, yielding a tiny newborn weighing less than 1 g, and with minimal maternal investment other than that spent in milk production. In contrast, a pregnant cow has a gestation period of 9 months that yields a very large calf whose development has drawn heavily upon maternal bodily resources. If during drought, this may leave the cow in a severely depleted state, resulting in her death and then that of the milk-deprived calf. Thus this marsupial reproductive characteristic serendipitously favors success of the red kangaroo during drought.

Thomas Newsome has masterfully polished his father’s incomplete manuscript by adding appropriate photographs from Alan’s slide collection, maps scaled to geographic descriptions, and quantitative tables that document results and conclusions; these latter were derived largely from a series of articles Alan published between 1964 and 1973 (e.g., Newsome, 1971). Together, the authors provide an informative and provocative read about a truly remarkable mammal.

The final chapter (Ch. 7) is a reproduction of an article Alan published in the anthropological journal Mankind in 1980 that demonstrates the congruence of Aboriginal oral history (“mythology”) with Alan’s own intuitive and observational ecological conclusions concerning movement during drought of red kangaroos. During the course of his studies Alan was frequently in contact with Aboriginal people from the Aranda totemic group, whose mythological ancestor is Ara, the red kangaroo. Not only did Alan receive physical aid from some of these people, but they must also have shared bits of their ancestral mythology. In addition, Alan was greatly influenced by the writings of Ted Strehlow, a Central Australian anthropologist born and raised on an Aboriginal mission near Alan’s study area, and who spoke the Aranda dialect fluently. In particular, he was impacted by Strehlow’s book, Songs of Central Australia (1971), that included Aranda mythology about travels of the red kangaroo during drought between watering and feeding sites. According to Aboriginal legend, during non-drought conditions feeding and watering points were fairly readily available at sites along the northern base of the MacDonnell Ranges, and further out amongst the mulga woodlands; the kangaroos could readily travel overland between them. As drought ensued these watering points gradually dried up, forcing the kangaroos to travel progressively further out onto the open plains to find food and water at sites far distant from each other. This led to the mythological belief that the travel between such distant sites must have been through underground passages, enabling the kangaroos to avoid perhaps lethal surface conditions. Alan concluded that the mythological descriptions of many of these watering points matched where he had observed kangaroos feeding and drinking during and after drought, and that at least this part of Aboriginal mythology must be based upon a keen sense of ecological perception, enhancing Aboriginal access to their preferred protein source during demanding environmental circumstances.

In 1989, while on a research leave in Australia, my wife, son, and I had the great pleasure and privilege of accompanying Alan from Alice Springs around to the north slopes of the MacDonnell Ranges to see one of these totemic sites he had identified, and as described in Strehlow (1971); Alan felt comfortable in taking us there as all of the Aboriginal elders who had held the tribal secrets had passed on. It was a humbling experience to witness this congruity between Aboriginal mythology and ecological reality, particularly when, upon departing the site, a large red kangaroo crossed the track ahead of us. And, as Thomas Newsome so aptly states in his Preface to the book: “It remains a groundbreaking piece of work, a pioneering example of why ecologists and land managers alike should listen to, and learn from, Indigenous knowledge”.

I first met Alan at Adelaide University in 1966 during my initial sabbatical leave in Australia, while I was on a seminar junket from my host institution, Monash University near Melbourne. Alan, who was my junior by 3 years, immediately struck me as a warm, congenial and knowledgeable ecologist with whom I could readily become a close friend and colleague. Since then our paths had crossed many times, both during my numerous research leaves in Australia, and when he was our guest as Regents Professor of Ecology and Evolutionary Biology in my department at U.C. Irvine. During the latter period we interacted intensively both at professional and family levels. Although we never had the opportunity to collaborate directly in research, my work in Central Australia certainly was influenced by his many outstanding contributions. I have felt from the beginning, as I do today, that, in addition to a keen intellect, it was Alan’s ability to communicate with virtually anyone at his or her own level, whether it be a cattle station manager, an Aboriginal informant, a research colleague, a student, or a friend, that made him such a successful individual. These communication skills together with his high capacity for organization enabled him to complete successfully, even as a novice field ecologist, an enormous amount of important work. This book, then, should be read and appreciated as such and as a tribute to Alan Newsome, and it is appropriately dedicated to him by his son, Thomas. Alan, we miss you, Mate! DICK MACMILLEN, Professor Emeritus of Ecology and Evolutionary Biology, University of California, Irvine; 705 Foss Road, Talent, OR 97540, USA;

In a paper published last week in Nature Communications we explored relationships between top predators and lower order predators (mesopredators) across three separate continents. We found that top predators can suppress the abundances of mesopredators, but only when top predators occur at high densities over large areas. The results have important implications for understanding the ecological role of top predators, like dingoes and wolves, and for the conservation of ecosystems more broadly.

Top predators can suppress mesopredators by killing them, competing for resources and instilling fear, but it is unclear how suppression of mesopredators varies with the distribution and abundance of top predators at large spatial scales and among different ecological contexts. We suggest that suppression of mesopredators will be strongest where top predators occur at high densities over large areas. These conditions are more likely to occur in the core than on the margins of top predator ranges. We propose the Enemy Constraint Hypothesis, which predicts weakened top-down effects on mesopredators towards the edge of top predators’ ranges. Using bounty data from North America, Europe and Australia we show that the effects of top predators on mesopredators increase from the margin towards the core of their ranges, as predicted. Continuing global contraction of top predator ranges could promote further release of mesopredator populations, altering ecosystem structure and contributing to biodiversity loss.

Domestic dogs (Canis familiaris) have a near-global distribution. They range from being feral and free-ranging to owned and completely dependent on humans. All types of domestic dogs can interact with wildlife and have severe negative impacts on biodiversity. Here, we use IUCN Red List data to quantify the number of threatened species negatively impacted by dogs, assess the prevalence of different types of dog impact, and identify regional hotspots containing high numbers of impacted species. Using this information, we highlight key research and management gaps and priorities. Domestic dogs have contributed to 11 vertebrate extinctions and are a known or potential threat to at least 188 threatened species worldwide. These estimates are greater than those reported by previous assessments, but are probably conservative due to biases in the species, regions and types of impacts studied and/or reported. Predation is the most frequently reported impact, followed by disturbance, disease transmission, competition, and hybridisation. Regions with the most species impacted are: South-east Asia, Central America and the Caribbean, South America, Asia (excluding SE), Micro/Mela/Polynesia, and Australia. We propose that the impacts of domestic dogs can be better understood and managed through: taxonomic and spatial prioritisation of research and management; examining potential synergisms between dogs and other threatening processes; strategic engagement with animal welfare and human health campaigns; community engagement and education; and mitigating anthropogenic effects such as resource subsidies. Such actions are essential for threatened species persistence, especially given that human and dog populations are expected to increase both numerically and geographically in the coming decades.

On landscapes around the world, environmental change is bringing people and large carnivores together—but the union is not without its problems. Human–wildlife conflict is on the rise as development continues unabated and apex predators begin to reoccupy their former ranges. Further complicating matters, many of these species are now reliant on anthropogenic, or human foods, including livestock, livestock and other ungulate carcasses, and garbage.

Writing in BioScience, Thomas Newsome, of Deakin University and the University of Sydney, and his colleagues use gray wolves and other large predators as case studies to explore the effects of anthropogenic foods. They find numerous instances of species’ changing their social structures, movements, and behavior to acquire human-provisioned resources. For instance, in central Iran, gray wolves’ diets consist almost entirely of farmed chickens, domestic goats, and garbage.

Other instances of these phenomena abound. In a similar case in Australia, dingoes gained access to anthropogenic foods from a waste facility. The result, according to the authors, was “decreased home-range areas and movements, larger group sizes, and altered dietary preferences to the extent that they filled a similar dietary niche to domestic dogs.” Moreover, wrote the authors, “the population of subsidized dingoes was a genetically distinct cluster,” which may portend future speciation events. Hybridization among similar predator species may also contribute to evolutionary divergence: “Anthropogenic resources in human-modified environments could increase the probability of non-aggressive contact” between species. According to the authors, “If extant wolves continue to increase their reliance on anthropogenic foods, we should expect to observe evidence of dietary niche differentiation and, over time, the development of genetic structure that could signal incipient speciation.”

Wolves’ use of anthropogenic food could have serious implications for wider conservation efforts, as well. In particular, Newsome and his colleagues raise concerns about whether wolf reintroduction and recolonisation programs will meet ecosystem-restoration goals in human-modified systems. Managers will need to consider “how broadly insights into the role played by wolves gleaned from protected areas such as Yellowstone can be applied in areas that have been greatly modified by humans,” say the authors.

Newsome and his colleagues call for further research—in particular, “studies showing the niche characteristics and population structure of wolves in areas where human influence is pervasive and heavy reliance on human foods has been documented.” Through such studies, they argue that “we might be able to ask whether heavy reliance of anthropogenic subsidies can act as a driver of evolutionary divergence and, potentially, provide the makings of a new dog.”

A conceptual model describing the role of anthropogenic foods in the hypothesized original wolf domestication pathway (left) and possible evolutionary divergence (right) due to behavioral and genetic differentiation. Silhouettes are courtesy of Phylopic (Tracy A. Heath).